The present invention relates to a gel chromatographic method whereby polar solvent-soluble polymers can be fractionated according to molecular weight and colloidal particles can be fractionated according to particle size. The two kinds of fractionation can be accomplished simultaneously. The invention also concerns particular surface-bonded particles and the process for making these coated particles which make the above fractionations possible.
The fractionation of colloidal particles, i.e., particles from about 100 Angstrom units diameter to as large as 5 to 10 microns in size, dispersed in a liquid medium according to particle size has been accomplished previously by passing the dispersion through a porous bed of finely divided solid such as very small beads of glass or insoluble resin, see Small, U.S. Pat. No. 3,865,717. However, there is often loss of some or even all of the colloidal particles to the column packing when the particle size of the packing is made smaller in an effort to increase the efficiency of the fractionation.
The application of gel permeation chromatography to the fractionation of water-soluble polymers by molecular weight requires mechanically stable column packing compatible with aqueous eluants and this application so far has been difficult and limited. Butler, U.S. Pat. No. 3,962,206 describes such an approach. Aqueous exclusion chromatography using glass beads of controlled porosity as a column packing has been used with some success in this area. However, many problems such as molecular weight range limitations and the adsorption of polycations, many polyampholytes and nonionic polymers to the column's substrate remain to be solved.